Don't confuse hardwired speeds with wireless speeds. Look at the speed of your main wireless router gets. Then see what the drop off is with the mesh. With the Orbi RBK50 I see no noticeable drop off. Actually when I ditched the Comcast modem/wireless router for a basic cheap Netgear modem and Orbi mesh my wireless speed when up.
1. Basic comcast (and verizon) modem/wireless routers suck. No one should be using them.
2. You only have ~100mbps speed.When you're dealing with gigabit speeds, the dropoff is more considerable. But there's no reason he shouldnt be getting 2-300 all over.
3. Yes - important to isolate what the issue is. What speed is the hardwired router getting? If you were to connect to the main router with a wired connection, what speed do you get? How about wireless 5-10 feet away? What speeds are the satellites getting? Are they hardwired or wireless? If you were to connect to the satellite with a wired connection, what speed do you get? How about wireless 5-10 feet away? How about 50 feet away?